European patent application EP 1 964 817 to Corning Inc. teaches a method for fabricating microfluidic devices made from glass, ceramic or vitroceramic, by die casting of the material containing glass with heating to make the material viscous and to shape it to define a sheet having an open structure face provided to constitute a microfluidic channel. To produce the casting of this structured surface to form the microfluidic channel, a rigid mould is used, for example made from a graphite block (see the fabrication method of the mould and of the glass sheet, paragraphs [0044] and [0045]).
This document also describes the assembly of a plurality of microfluidic sheets comprising structured surfaces sealed together at 800° C. in air to constitute the microfluidic device (see paragraph [0047] to [0049]).
This microfluidic device made from glass, ceramic or vitroceramic can be used as a small-volume chemical reactor. The micro-processing chamber defined by a microfluidic channel is obtained by combining at least two glass, ceramic or vitroceramic layers or sheets sealed together.
It is therefore very important for the seal to be perfectly tight and for the two sheets or layers to be perfectly or nearly perfectly aligned during their stacking upon one another.
The sealing between the two glass, ceramic or vitroceramic sheets or layers stacked up on one another is generally carried out by depositing a glass, ceramic or vitroceramic frit on the surface to be sealed, followed by a thermal cycle to produce the viscous flow of the frit layer on the surface of the structures to be sealed and to remove the organic products which are generally present in the frit formulation.
A microfluidic device according to this document is shown in appended FIG. 1.
In addition to a proper alignment of the layers to be sealed, it is necessary to have a uniform coating of the surface to be sealed, in particular at the protuberances defining the sides of the microfluidic channel.
Document WO 2005/090227 also teaches a stack structure and a method for fabricating the same.
According to this document, the stacking of the micro-reactors 2 defining microchannels 2c is carried out by means of the combination of an electrically conducting buffer film and a layer in the form of a metal or metal alloy bonding film, for producing a bond by oxidation of the metal or of the alloy by the oxygen atoms contained in the glass structure 2 (see page 8, line 5 to pages 9 and 11), in particular. This oxidizing method is called an anode bonding method. This document proposes a solution which is very costly and which introduces the use of metals or alloys in a structure of microfluidic devices, whereas in the context of this disclosure, glass, ceramic or vitroceramic compositions are used essentially or exclusively, and the use of metal or alloy is to be avoided.
Document U.S. Pat. No. 6,600,558 B2 constitutes another document which describes the fabrication of a microfluidic cell for the optical detection of gas, which combines layers of glass such as Pyrex, which are sealed together, by means of a silicon nitride film by an anode bonding method (see column 8, lines 8 to 53 in particular).
Once again, the present disclosure is aimed to eliminate this type of fabrication which requires bonding by an anode method.
It is desirably to supply of a microfluidic device via a solution that allows an easy alignment of the open structures to be sealed, and which culminates in a uniform coverage of the surface of the protuberances of the processing microchannels.